The adhesives nowadays used for rubber to metal bonding are either based on silane coupling agents (see is "Silane Coupling agents", F. P. Plueddemann, Plenum Press, New York, 1990) or a mixture of resins, elastomers and fillers which suspended or dissolved in organic solvents (see "Rubber to metal bonding", P. M. Lewis in Handbook of Adhesion, D. E. Packham(ed.), Longman Scientific & Technical, Harlow, 1992). A specific kind of adhesion promoter is a galvanic layer of brass, mainly used in tire cord applications (see W. J. van Ooij, Rubber Chem. Technol., 52, 4.37 (1979)). Most of the adhesives are applied in a two layer system which contains an adhesive layer and a primer layer to obtain durable joints with high chemical resistance, thermal stability and hydrolytical stability. There are still some problems to achieve the required properties in specific rubber to metal adhesion with the adhesives.
Coupling agents are defined as materials that improve adhesion by forming primary bonds to the substrates, applied coatings, or composite materials. The silane coupling agents usually incorporate three hydrolyzable groups and another reactive group on silicon. The hydrolyzable groups are essential when applied to inorganic substrates, whereas the other reactive group is able to react with organic substrates. The main applications of silane coupling agents are in the technology of composites, the paint industry, and in the case of rubber to metal bonding such as the bonding of fluororubbers to metal substrates. It is noted that various organofunctional silanes and a few non-silane coupling agents such as methylacrylate-chrome complex (Volan A) have shown promise as true coupling agents. However, some cases such as the adhesion of EPDM rubber with stainless steel have not been investigated with the silane coupling agents.
Accordingly, it is an object of the present invention to provide novel polymeric coupling agents which will be used as adhesives for the adhesion of some dissimilar substrates such as rubbers with metals.
It is another object of the invention to provide polymeric coupling agents which can be applied in preferred solvents such as water and ethanol.
It is still another object of the invention to provide polymeric coupling agents which incorporate within their structures metal-complexing groups as well as co-vulcanizable groups.
It is a further object of the invention to provide methods of synthesizing the novel polymeric coupling agents.
It is still a further object of the invention to provide methods of using the novel polymeric coupling agents for the adhesion of macromolecular materials with metal substrates, and particularly for the adhesion of rubbers with metals.